Recently, multi-display devices have been proposed in which image display devices are arranged vertically, horizontally, or vertically and horizontally. In each of the image display devices, a light-transmittance adjustment device adjusts light transmittance for light emitted from an image-display light-emitting device, whereby an image is formed. Each of the image display devices forms an image corresponding to its arranged position, whereby the multi-display devices display a large-screen image.
In the multi-display devices, uneven brightness between images displayed by the individual image display devices worsens the continuity of the images, and consequently the viewer feels a sense of inconsistency. Accordingly, there are multi-display devices that adjust light emitted from image-display light-emitting devices included in corresponding image display devices so as to have the same brightness in all the image display devices (see, for example, Japanese Patent No. 4044930).
The image-display light-emitting device is a device that emits light of certain brightness. A transmittance adjustment device (for example, liquid crystal) included in the image display device adjusts light transmittance. In this way, an image is displayed. However, with the configuration of emitting light of certain brightness, such as the image-display light-emitting device, light emitted from the image-display light-emitting device needs to be blocked by the light-transmittance adjustment device when a black image is displayed. This often decreases the contrast ratio of the image.
Liquid crystal display devices are sometimes used as the image display devices. Liquid crystal display devices include a liquid crystal panel and a backlight serving as the image-display light-emitting device. In liquid crystal display devices, light transmittance for light emitted from the backlight is controlled by the liquid crystal panel, whereby an image is displayed. An example of such a backlight is a device including light-emitting elements provided in multiple divided areas of a plate-shaped member that is arranged to oppose the liquid crystal panel. There is a type (hereinafter, sometimes referred to as an “area-driven type”) that controls light emission of the light-emitting elements provided in the individual areas on an area-by-area basis.
An area-driven type backlight is capable of adjusting brightness of the backlight (in other words, power supplied to the light-emitting elements of the backlight) on an area-by-area basis in accordance with image data. That is, the area-driven type backlight is capable of performing adjustment to make light-emitting elements belonging to an area brighter as an image of the corresponding portion is brighter and make the rest of the light-emitting elements darker. Consequently, an image with a high contrast ratio can be obtained. As the light-emitting elements of the backlight, elements that emit light (that change light emission brightness) in accordance with supplied current (power), notably LEDs, are used in most cases.
Also, in the liquid crystal display devices, a certain limit power value is set for power consumption of the backlight because of demands for reduced power consumption, reduced heat generation, and so forth. Some liquid crystal display devices control driving of the backlight so that the light emission power value of the backlight does not exceed the limit power value.
Liquid crystal display devices including such an area-driven-type backlight can obtain an image with a high contrast ratio (with peak brightness) while suppressing power consumption thereof. By constituting a multi-display device by sequentially arranging such liquid crystal display devices, a large-screen image with a high contrast ratio (with peak brightness) can be displayed while suppressing the power consumption.